Detailed analysis of the effect of parallel lines on the impedance seen by the traditional ground distance function

摘要

This study analyses the effect of parallel lines on the impedance seen by the traditional ground distance function. Different pre-fault load flows, system impedances and fault resistances are considered, as well as the possible connections of the parallel line (in parallel, in open-circuit or short-circuited at both line ends). Cases with and without compensation for the mutual impedance of the parallel line are considered, as well as cases with and without adaptive change of relay settings. In general, the results are highly dependent on the connection of the parallel line. System impedances have more influence on the results than the pre-fault load flow. On the other hand, the maximum fault resistance that can be seen by the distance function is moderately influenced by the effect of the parallel line. Thus, this exhaustive analysis shows the relative importance of each relevant factor (pre-fault load flow, system impedances, fault resistances, parallel line connectivity, and possible use of compensation for mutual impedances). A similar analysis about this topic was not available in the literature, and this knowledge is useful for the recommendations about the setting of the traditional ground distance function by considering the effect of parallel lines.